appserver/tests/appserv-tests/devtests/web/servlet-4.0/compositeTrailerSupplier/servlet/TestFilter.java

/*
 * Copyright (c) 1997, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

import java.io.IOException;

import java.util.HashMap;
import java.util.Map;
import java.util.function.Supplier;

import jakarta.servlet.Filter;
import jakarta.servlet.FilterChain;
import jakarta.servlet.ServletException;
import jakarta.servlet.ServletRequest;
import jakarta.servlet.ServletResponse;
import jakarta.servlet.annotation.WebFilter;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

@WebFilter("/mytest")
public class TestFilter implements Filter {
    @Override
    public void doFilter(ServletRequest req, ServletResponse res,
            FilterChain chain) throws IOException, ServletException {

        if (res instanceof HttpServletResponse) {
            HttpServletResponse httpRes = (HttpServletResponse)res;
            httpRes.setTrailerFields(new Supplier<Map<String, String>>() {
                @Override
                public Map<String, String> get() {
                    Map<String, String> map = new HashMap<>();
                    map.put("bar1", "A");
                    System.out.println("--> supplier return: " + map);
                    return map;
                }
            });
        }
        chain.doFilter(req, res);
    }
}